1. Field of Invention
The present invention relates to the technical field of advanced materials, and particularly to a method for preparing graphene from a biomass-derived carbonaceous mesophase.
2. Description of Related Arts
Graphene is a one-atom thick layer of a two-dimensional carbon atom crystal and shapes like a hexagonal honeycomb. It is considered to be the basic structural element of fullerenes, carbon nanotubes, and graphite: if decomposed, the graphene becomes a zero-dimensional fullerene; if curled up, the graphene becomes a seamless hollow tube, namely, a one-dimensional nanotube; and if stacked in a parallel way, the graphene becomes three-dimensional bulk graphite. Since the discovery of the single-layer graphene in 2004, with a series of good physical and chemical properties such as its unique optical property, outstanding thermal conductivity and mechanical property, and extraordinary electron conduction performance, graphene has attracted wide attention and great interests of scientists.
Current graphene preparation methods mainly include mechanical exfoliation, epitaxial growth on SiC or metal substrates, graphite oxide reduction, chemical vapor deposition, and the like. In mechanical exfoliation, graphene wafers are repeatedly exfoliated from highly oriented pyrolytic graphite through a transparent photoresist. The method has a small yield, is low in production efficiency and poor in repeatability, and is limited to the production in laboratory only. By means of epitaxial growth on SiC, large-area and high-quality graphene wafers can be prepared, but the preparation conditions require high temperature and high vacuum, which results in high costs of raw materials and process control. The chemical vapor deposition uses carbon-containing compounds as a carbon source, decomposes the carbon source on the metal base at a high temperature, and deposits the decomposed carbon source on the surface of the base; the obtained graphene wafer is spliced by small sized graphene flakes, and the presence of crystal boundary affects the performance of graphene.
According to the research on the prior art documents, the Patent Publication No. CN 102409399A discloses a method for preparing high-quality graphene, in which a graphene wafer formed by opening single-walled or multi-walled carbon nanotubes is used as a seed crystal, and by means of chemical vapor deposition, graphene is grown on the substrate surface with the seed crystal as a core. This method prepares a large-scale and low-defect graphene material, but uses an expensive raw material, namely the carbon nanotube, which is also short of sources. Besides, the carbon nanotubes need to be opened through ion etching or chemical oxidization to form graphene as a seed crystal, which increases the complexity of the experiment process.
The Chinese Patent Publication No. CN 1421477A discloses a method for preparing an optically anisotropic carbonaceous mesophase by using a biomass resource material and waste thereof as raw materials and performing a serious of processing thereon. The biomass-derived carbonaceous mesophase has abundant sources, is cheap and environmental-friendly, and is applicable to mass industrial production. Moreover, different from the carbonaceous mesophase produced with petroleum and coal as raw materials, the biomass-derived carbonaceous mesophase has a larger inter-layer spacing. There have been a lot of reports about the preparation of graphite from the carbonaceous mesophase produced with petroleum and coal as raw materials, so the biomass-derived carbonaceous mesophase can be used as a precursor to prepare graphene.